Optimized radiochemistry and clinical evaluation of Tc-99m-hexakis (T-butylisonitrile)-technetium(I)cation(Tc99m-TBI): a potential myocardial perfusion tracer

For the preparation of sup(99m)Tc-TBI, ligand exchange (a) and direct reductive complex formation from TcO4-(b) were studied. HPLC analysis (RP C18) revealed a 2nd sup(99m)Tc compound from (a) only; therefore, reaction conditions for (b) were optimized in a parameter study. Finally sup(99m)Tc-TBI was obtained at 97 % yield and purified from ligand by prep HPLC or Sep Pak C18. Biodistribution in mice showed rapid blood clearance, initial high uptake in lungs and prominent persisting activity in liver and heart. Clinical studies showed a corresponding pattern in patients yielding high-quality myocardial scintigrams at and after 1 hour p.i.. Liver activity was the main interference, especially in the inferior apical region. In resting studies transmural infarction was seen as reduced accumulation, whereas non-transm. inf. and ischemic regions were only detected after stress. In contrast to 201Tl these stress-induced perfusion defects persisted for 6 hrs. The compound deserves further clinical evaluation. (Author)